Over the last 3 years shippers have quietly been raising their prices in the US through the roof, and nobody notices until they have to buy or ship something and then they are shocked. It's not just the postal service, but all shippers have price matched each other.
Most companies that sell a lot of merchandise have special contracts that allow for huge discounts in shipping costs. If you are buying from a company online that charges high prices for shipping even though they sell a lot of merchandise, they are probably ripping you off. Try shopping around on web sites like Amazon.com where you can often find free shipping and lower prices on the very same items.